Effects of oestrogens and pregnancy on the distribution of sheep erythrocytes and the antibody response in mice.

Mice pre-treated with three oestrogenic preparations showed increased hepatic and reduced splenic uptake of 51Cr-labelled sheep erythrocytes (SRBC). The anitbody response to SRBC wahe number of antibody-forming cells in the spleen parallels the amount of SRBC localizing in this organ and that both can be depressed or enhanced by appropriate pre-treatments with oestrogens or colloidal carbon. The effects of these agents are mediated through stimulation or 'blockade' of the phagocytic activity of liver macrophages. Changes in localization of SRBC in pregnant mice were similar to those found after treatment with oestrogens. These changes were, however, rather small and the antibody response of pregnant animals was not affected.